PaletteEdit: temporary custom gradient not saving (#56896)

* Gradient elements contain both color and gradient properties, therefore they'll always return true for this test if the color property is default (#000)

* CHANGELOG.md

* isTemporaryElement should return false by default so that it will catch changes to the slug
Added tests

packages/components/CHANGELOG.md

@@ -13,7 +13,7 @@
 -   `FontSizePicker`: Add opt-in prop for 40px default size ([#56804](https://github.com/WordPress/gutenberg/pull/56804)).
 
 ### Bug Fix
-
+-   `PaletteEdit`: temporary custom gradient not saving ([#56896](https://github.com/WordPress/gutenberg/pull/56896)).
 -   `ToggleGroupControl`: react correctly to external controlled updates ([#56678](https://github.com/WordPress/gutenberg/pull/56678)).
 -   `ToolsPanel`: fix a performance issue ([#56770](https://github.com/WordPress/gutenberg/pull/56770)).
 -   `BorderControl`: adjust `BorderControlDropdown` Button size to fix misaligned border ([#56730](https://github.com/WordPress/gutenberg/pull/56730)).

packages/components/src/palette-edit/index.tsx

@@ -60,7 +60,7 @@ import type {
 	PaletteElement,
 } from './types';
 
-const DEFAULT_COLOR = '#000';
+export const DEFAULT_COLOR = '#000';
 
 function NameInput( { value, onChange, label }: NameInputProps ) {
 	return (
@@ -261,16 +261,30 @@ function Option< T extends Color | Gradient >( {
 	);
 }
 
-function isTemporaryElement(
+/**
+ * Checks if a color or gradient is a temporary element by testing against default values.
+ */
+export function isTemporaryElement(
 	slugPrefix: string,
 	{ slug, color, gradient }: Color | Gradient
-) {
+): Boolean {
 	const regex = new RegExp( `^${ slugPrefix }color-([\\d]+)$` );
-	return (
-		regex.test( slug ) &&
-		( ( !! color && color === DEFAULT_COLOR ) ||
-			( !! gradient && gradient === DEFAULT_GRADIENT ) )
-	);
+
+	// If the slug matches the temporary name regex,
+	// check if the color or gradient matches the default value.
+	if ( regex.test( slug ) ) {
+		// The order is important as gradient elements
+		// contain a color property.
+		if ( !! gradient ) {
+			return gradient === DEFAULT_GRADIENT;
+		}
+
+		if ( !! color ) {
+			return color === DEFAULT_COLOR;
+		}
+	}
+
+	return false;
 }
 
 function PaletteEditListView< T extends Color | Gradient >( {

packages/components/src/palette-edit/test/index.tsx

@@ -6,8 +6,13 @@ import { render, fireEvent, screen } from '@testing-library/react';
 /**
  * Internal dependencies
  */
-import PaletteEdit, { getNameForPosition } from '..';
+import PaletteEdit, {
+	getNameForPosition,
+	isTemporaryElement,
+	DEFAULT_COLOR,
+} from '..';
 import type { PaletteElement } from '../types';
+import { DEFAULT_GRADIENT } from '../../custom-gradient-picker/constants';
 
 describe( 'getNameForPosition', () => {
 	test( 'should return 1 by default', () => {
@@ -80,6 +85,75 @@ describe( 'getNameForPosition', () => {
 	} );
 } );
 
+describe( 'isTemporaryElement', () => {
+	[
+		{
+			message: 'identifies temporary color',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-color-1',
+				color: DEFAULT_COLOR,
+			},
+			expected: true,
+		},
+		{
+			message: 'identifies temporary gradient',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-color-1',
+				gradient: DEFAULT_GRADIENT,
+			},
+			expected: true,
+		},
+		{
+			message: 'identifies custom color slug',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-color-happy',
+				color: DEFAULT_COLOR,
+			},
+			expected: false,
+		},
+		{
+			message: 'identifies custom color value',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-color-1',
+				color: '#ccc',
+			},
+			expected: false,
+		},
+		{
+			message: 'identifies custom gradient slug',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-gradient-joy',
+				color: DEFAULT_GRADIENT,
+			},
+			expected: false,
+		},
+		{
+			message: 'identifies custom gradient value',
+			slug: 'test-',
+			obj: {
+				name: '',
+				slug: 'test-color-3',
+				color: 'linear-gradient(90deg, rgba(22, 22, 22, 1) 0%, rgb(155, 81, 224) 100%)',
+			},
+			expected: false,
+		},
+	].forEach( ( { message, slug, obj, expected } ) => {
+		it( `should ${ message }`, () => {
+			expect( isTemporaryElement( slug, obj ) ).toBe( expected );
+		} );
+	} );
+} );
+
 describe( 'PaletteEdit', () => {
 	const defaultProps = {
 		colors: [ { color: '#ffffff', name: 'Base', slug: 'base' } ],